Phenol is an important chemical having a wide variety of uses. Included among these is the preparation of adipic acid, a nylon precursor. Utilization of phenol for this and other uses is increasing. Phenol is currently derived principally from petroleum. Due to the potentially increasing scarcity and cost of petroleum, alternative sources therefor are highly desirable.
It is known that polymeric aromatic compounds, particularly peat, coal and lignin, which are in relatively abundant supply, can be depolymerized to yield varying amounts of mixed phenols. Coal is a complex, multi-ring, aromatic polymer with varying relative amounts of carbon, oxygen and hydrogen. Of most significance to phenol production are bituminous, sub-bituminous and lignite coals. Coal depolymerization techniques include liquefaction, gasification and pyrolysis.
Lignin is essentially a polyphenol having a high oxygen content. It is derivable from biomass, i.e., renewable resources such as trees, agricultural products and municipal waste, by a variety of processes. These include, e.g., the well-known Kraft process and acidic hydrolysis. The exact composition of lignin so derived, and hence possibly the desirability of the lignin for use in producing phenols, depends upon both the source of the lignin and the manner in which it is derived therefrom.
Mixed phenols derived from coal and biomass can, depending on the source and the depolymerization process, comprise phenol, cresols, xylenols and higher alkyl and polyalkyl phenols, such as ethyl phenol and propyl phenol, in varying relative amounts. Reported or projected mixed phenol compositions from various coal and lignin sources by various depolymerization techniques appear in Table 1, which follows, in weight percent. In the first column, the mixed phenols are reported as weight percents of all crude tar acid products. In the other columns, they are reported as weight percents of all mixed phenol products.
TABLE 1 ______________________________________ Gasification Lique- Hydro- S. Afr. subbitum- faction cracking (SASOL) inous Bituminous Kraft Coal.sup.1 Coal.sup.2 Coal.sup.3 Lignin.sup.4 ______________________________________ phenol 38 18 38 7 o-cresol 8 9 10 4 m-, p-cresol 14 16 31 22 xylenols 13 14 9 7 other alkyl phenols 16 42 12 61 ______________________________________ .sup.1 Hoogendoorn, J.C. IGT Symposium Papers on Clean Fuels from Coal, Sept. 1973, page 111. .sup.2 Frank, M.A., IGT Symposium Papers Advance in Coal Utilization Technology III, May 1979, page 727. .sup.3 Gulf Mineral Resources Company, personal communication. .sup.4 Parkhurst, H.J., et al., Symposium on Alternate Feedstocks for Petrochemicals, ACS Meeting, Las Vegas, Neveda, August 1980.
Various dealkylation procedures for converting such mixed phenols to phenol are known. These include thermal dealkylation procedures such as are disclosed in the following: U.S. Pat. No. 4,230,895 which discloses a process for thermal hydrodealkylation of mixed alkyl phenols; U.S. Pat. No. 3,284,513 which discloses a process for thermal hydrodealkylation of monoalkylated phenols; and U.S. Pat. No. 3,284,514 which discloses a process for thermal hydrodealkylation of polyalkylated phenols. The Hydrocarbon Research, Inc. Dynaphen process, Chem. and Eng. News, Nov. 30, 1981, pages 32,34, is an example of a thermal dealkylation procedure using coal liquids.
U.S. Pat. No. 4,191,844 discloses a catalytic process for hydrodealkylating certain aromatic compounds in a single vessel, in which process the catalyst contains manganese oxide and a Group IIA metal oxide for dealkylation and transalkylation; a Group VIII metal oxide, such as nickel oxide, to allow dealkylation at lower temperature; and alumina or silica-alumina containing a major amount of alumina for isomerization of m-cresol to o-cresol. The patent further discloses that cresols and xylenols can be derived from coal.
U.S. Pat. No. 4,189,613 discloses catalytic hydrodealkylation of certain aromatic compounds in which the catalyst is a low sodium-content chromia on alumina.
U.S. Pat. No. 4,436,945 discloses catalytic hydrodealkylation of alkyl aromatic compounds using a zeolite catalyst wherein 15 to 50 equivalent % of exchangeable cations have been exchanged for hydrogen ions.
U.S. Pat. No. 4,405,812 discloses a process for dealkylating ortho-alkylated aromatic amines at elevated temperatures using a nickel catalyst, optionally supported on oxides, including silica, Kieselguhr, silica-alumina, alumina and magnesia.
Catalytic dealkylation procedures also include processes such as are disclosed in the following: Kadlec, J. and Bazant, V., Coll. Czech. Chem. Comm., 26, 1201-1203 (1961), which discloses dealkylation of o-ethyl and o-propyl phenols by catalytic hydrogenation; Jost. F. and Bazant, V., ibid., 3020-3027, which discloses demethylation of cresols; and Beranek, L., et al., Coll. Czech. Chem. Comm., 29, 239-249 (1964), which discloses dealkylation of various mono- and dialkyl phenols.
In the above-cited paper by Jost, F. and Bazant, V., it is disclosed that o-cresol is more highly reactive than m- and p-cresol. Publications disclosing demethylation of o-cresol include Jost and Bazant, supra; Weidenhoffer, Z., et al., Coll. Czech. Chem. Comm., 32, 3746-3756 (1967); Kadlec, J., et al., Coll. Czech. Chem. Comm., 26, 818 (1961); and Czechoslovakian Patent 99012, the latter disclosing a process for preparing a nickel-Group II, III or IV metal catalyst which is useful in dealkylating alkyl phenols.
U.S. Pat. No. 4,283,571 discloses a process for isomerizing o-cresol to m-cresol by contacting the o-cresol with a crystalline aluminosilicate zeolite of the ZSM type.
U.S. Pat. No. 4,465,892 discloses isomerization of hydrocarbons at a temperature of 100.degree.-300.degree. C. using a catalyst comprising a Group VIII metal supported on a bridged clay.
U.S. Pat. No. 4,503,269 discloses an improved process for isomerizing cresols in the presence of a crystalline aluminosilicate zeolite catalyst and added hydrogen, at a temperature in the range 250.degree. C. to 450.degree. C. and a pressure in the range of 2 to about 75 atmospheres. Hydrogen is present in a H.sub.2 /cresol mole ratio of about 1:1 to about 10:1. The isomerization of o-cresol to m- and p-cresols is emphasized and there is no showing or suggestion of enrichment of o-cresol.
U.S. Pat. No. 4,452,915 discloses a process for selective o-alkylation of phenols with a lower alkane in the presence of a supported nickel oxide catalyst. Supports include alumina, silica and Kieselguhr.
It is an object of this invention to provide a process for preparing phenol from mixed phenols. It is also an object to provide a process for preparing phenol from mixed phenols derived from coal and biomass. It is a further object of this invention to provide a process for preparing adipic acid from mixed phenols, such as may be derived from coal and biomass.